1. Field of the Invention
The present invention relates to an optical lithography using a photocurable component for producing a three-dimensional article.
2. Background Art
Optical lithography, as indicated by the name, in a method comprising successively scanning a liquid photocurable component with a laser beam without using a mould at all, and curing/laminating resin layers to eventually produce a three-dimensional article (Yoji Maritani, et al., xe2x80x9cOptical Lithography-Three-Dimension Plotter using Laserxe2x80x9d, Nikkan Kogyo Newspaper). According to this method, for example, formed articles such as a skull model that could be made by utilizing results of CT scanning, which are unable to be made by the conventional extrusion or other plastic forming, can be made with perfect ease. Furthermore, with the background of the rapid prototyping receiving much attention at home and abroad in recent years, the optical lithography has become one of the typical forming methods.
Herein, more specifically describing the optical lithography, according to this optical lithography, the formation of a three-dimensional article is carried out by pattern irradiation of light on the surface of a resin composition for optical lithography contain a photocurable component in order to form a cured resin layer corresponding to the pattern, and lamination of such layers to form the three-dimensional shape with a plurality of such cured resin layers. Therefore, a three-dimensional article is formed by analyzing a three-dimensional shape of the article with a computers preparing and accumulating a plurality of data of sliced parts of the shape, radiating ultraviolet laser on a surface of each layer of resin composition for optical lithography according to the data of each layer in the order, and thereby forming photocured resin composition layers one after another.
For example, in the Japanese Patent Laid-open Publication No. Sho56-144478, a method for forming a three-dimensional article has been disclosed, wherein the method comprises placing a liquid photocurable component in a vessel, selectively irradiating the surface of the photocurable component by scanning an exposure means provided on the upper part of the vessel to form a cured resin layer, supplying the photocurable component for one layer over this cured rein layer to form a liquid resin layer, selectively irradiating the surface thereof with light to laminate a fresh cured resin layer as a unit over the previously formed cured resin layer was to continue with each other, and repeating the supply of the photocurable component and irradiation with light predetermined times.
In the conventional optical lithography apparatuses, usually using the ultraviolet laser, a selective drawing of pattern is arranged to be performed for every layer in a rater scanning system. However, in this method, there are problems such as non-uniform resin shrinkage and non-uniform curing depth in cured layers caused by scanning intervals and power instability of laser. Furthermore, there is also another problem that, due to the curing/shrinkage characteristics of rein, shrinkage occurs somewhat after the laser drawing so that shrinkage proceeds with time according to the laser drawing traces, resulting in the generation of internal stress to become liable to form warps in cured layers.
Furthermore, there is yet another problem that, due to not only the low energy efficiency of laser but also especially a short life time of a laser generator to emit the ultraviolet ray required to cure the photocurable component, the continuous and large-scale forming of articles by optical lithography is disadvantageous in terms of cost.
Thus, there has been proposed a method for selectively irradiating the surface of photocurable component through a predetermined mask pattern with the parallel ultraviolet ray emitted from a mercury lamp, etc. For example, in the Japanese Patent Laid-open Publication No. Hei2-78531, as a method for selectively irradiating the surface of photocurable component with light, a method for exposing the surface to light through a mask pattern, which selectively transmits light, has been disclosed.
However, in such a method using mask, there in a problem that said method is uneconomical after all because of the requirement of a great number of mask patterns. In addition, there is another problem that the light diffraction occurs at the time of light transmission through the mask to blur the designed pattern so that the pattern with fine precision cannot be formed. Furthermore, a large number of mask patterns are generally prepared by drawing each of them with toner every one layer on a transparent glass plate, or by forming a pattern every one layer with the liquid crystal shutter. In these cases, there are problems that ultraviolet ray cannot be completely shut out at critical portions, and also that the liquid crystal and glass plate tend to be worn out with ultraviolet ray so that they cannot stand a long-term use and are not suitable for forming articles by optical lithography on a large scale.
In view of the above-described problem, the present invention has been made aiming at providing an optical lithography using a mask pattern for producing a large quantity of three-dimensional articles rapidly with high precision.
In order to solve the above-described problems, an optical lithography according to this invention is characterized in that a predetermined mask pattern is drawn directly on the surface of a resin composition for optical lithography to be irradiated from above with light, thereby preventing the decline in precision due to the diffraction of irradiation light, and in that a resin composition for optical lithography is further laminated to be photocured without removing the mask pattern, thereby overcoming difficulties in the adjustment of photocuring in the depth direction that have been the drawback in optical lithography.
Optical Lithography According to this Invention
More specifically, the present invention provides the following optical lithography.
(A1) An optical lithography for forming a three-dimensional article composed of multiple cured resin layers by irradiating light over a mask pattern previously drawn on a surface of a resin composition for optical lithography containing a photocurable component, and repeating such irradiating step to form a cured resin layer corresponding to the drawn pattern, wherein the lithography is characterized by the light irradiation over the predetermined mask pattern that is drawn directly on the surface of the resin composition for optical lithography. In this invention, the rapid gelation described below may be preferable, but is not essential (methods according to the procedures described in Japanese Patent Laid-open Publication No. Hei9-70897, Japanese Patent Laid-open Publication No. Sho56-144478, etc. may be applied: that is, a method of irradiating a resin composition for optical lithography over a mask pattern drawn directly on the composition after solidifying the resin composition by cooling it below a room temperature and a method of irradiating light over a mask pattern directly drawn on a surface of the resin composition while it still has fluidity.).
(A2) An optical lithography for forming a three-dimensional article composed of multiple cured resin layers by irradiating light over a mask pattern previously drawn on a surface of a resin composition for optical lithography containing a photocurable component, and repeating irradiating step to form a cured resin layer corresponding to the drawn pattern, wherein the optical lithography is characterized in that a resin composition capable of making a reversible and rapid sol-gel phase transition with some physical stimulus is employed as the resin composition for optical lithography, and wherein the optical lithography comprises gelating rapidly the resin composition for optical lithography by applying xe2x80x9csome physical stimulusxe2x80x9d, directly drawing a mask pattern on the surface of the gelated resin composition for optical lithography, and irradiating light over the mask pattern.
(A3) An optical lithography comprising supplying a one-layer amount of resin composition for optical lithography containing a photocurable component, which is capable of making a reversible and rapid sol-gel phase transition with some physical stimulus, to form the nth resin layer, gelating the nth resin layer with some physical stimulus, drawing a predetermined mask pattern directly on the gelated nth resin layer, forming the nth cured resin layer by irradiating the nth resin layer with light over the mask pattern to photocure the nth resin layer according to the mask pattern, and supplying the resin composition for optical lithography for one layer over the nth cured resin layer to form the (n+1)th resin layer.
(A4) An optical lithography as described in any one of the above (A1) through (A3), wherein the optical lithography is characterized in that the xe2x80x9csome physical stimulusxe2x80x9d is a temperature change.
(A5) An optical lithography as described in any one of the above (A1) through (A4), wherein the resin composition for optical lithography contains a photocurable component comprising urethane acrylate series, ester acrylate series, epoxy acrylate series, or epoxy series.
(A6) An optical lithography as described in any one of the above (A1) through (A5), wherein the resin composition for optical lithography comprises a photocurable component, syndiotactic poly(methacrylic acid ester) and isotactic poly(methacrylic acid ester).
(A7) An optical lithography as described in the above (A6), wherein the resin composition for optical lithography contains photocurable components, syndiotactic poly(metylmethacrylate) and isotactic poly(metylmethacrylate).
Photocurable Component used in Optical Lithography
The photocurable component used in the optical lithography may include material also referred to as photosensitive resin, which is widely used, for example, as the resist at etching in the process of manufacturing semiconductors.
In an optical lithography according to this invention, as the photocurable component, either oligomer having one functional group or more per molecule capable of reacting to light irradiation to form a cross-linkage or monomer having one similar functional group or more per molecule, or both of them are used. Examples of the oligomers comprise radical polymerization type photocurable resins such as unsaturated polyester resins, acrylic resins, en-thiol resins, etc. or cation polymerization type photocurable resins such as epoxy resins (needles to say, besides these, for example, a mixture of novolac resin with a photosensitizer such as diazonaphtoquinone sulfonic acid ester may be used.) Among them, acrylic resin such as ester acrylate, urethane acrylate and epoxy acrylate in particular an preferable as the oligomers which are contained in resin compositions for optical lithography according to this invention. Examples of the above-described monomers are radical polymerization type monomers such as acrylic acid esters, methacrylic acid esters, etc. and cation polymerization type monomers such as epoxy-containing compounds, etc. Among them, radical polymerization type monomers are preferable in a view of the curing speed and post-curing physical properties thereof.
In addition, to promote the speedy occurrence of photoreaction, the resin composition for optical lithography may be prepared to contain a small amount of photosensitizers (such as nitro compounds, quinones and ketones, etc.). Furthermore, the resin composition for optical lithography according to this invention may comprise fillers (reinforcements), plasticizers, stabilizers, colorants, fire retardants, antioxidants or antistatic agents, etc.
Herein, resin compositions useable as the rein composition for optical lithography in an optical lithography according to this invention or resin composition preferable as the resin composition for optical lithography according to this invention are described as follows:
(B1) a resin composition for optical lithography comprising a photocurable component which solidifies by irradiation with light and a resin component of rapid phase transition capable of causing the phase transition sol to xe2x80x9cgel distinguishable from the photocured portionxe2x80x9d with some physical stimulus.
(B2) a resin composition for optical lithography comprising a photocurable component which solidifies by irradiation with light, and a resin component of reversible and rapid phase transition capable of causing a reversible as well as rapid sol-gel phase transition with some physical stimulus.
(B3) a resin composition for optical lithography as defined in the above (B2) characterized in that xe2x80x9csome physical stimulusxe2x80x9d may be a temperature change.
(B4) a resin composition for optical lithography as described in the above (B3) characterized in that the resin component of reversible rapid phase transition comprises a mixture of a syndiotactic poly(methyl methacrylate) and isotactic poly(methyl methacrylate).
(B5) a resin composition for optical lithography as described in the above (B4) characterized in that the photocurable component comprises a photocurable resin of the urethane acrylate series, ester acrylate series, epoxy acrylate series or epoxy series.
Definitions and Others
xe2x80x9cResin component of rapid phase transitionxe2x80x9d has been defined as xe2x80x9ca resin component of rapid phase transition capable of causing a phase transition xe2x80x9crapidly from sol with some physical stimulusxe2x80x9d to xe2x80x9cgel distinguishable from the photocured portionxe2x80x9d, or as xe2x80x9ca resin component of reversible rapid phase transition capable of causing a reversible and rapid sol-gel phase transition with some physical stimulusxe2x80x9d, which is a component expressing a property rapidly causing xe2x80x9cthe sol-gel phase transitionxe2x80x9d or xe2x80x9cgel-sol phase transitionxe2x80x9d by the physical interaction between the resin component of rapid phase transition and at least a portion of the photocurable component without showing such a xe2x80x9cglass transitionxe2x80x9d observed with usual resins when said resin component of rapid phase transition and photocurable component are mixed. More specifically speaking, ordinary resins, for example, gradually soften at and above the glass transition temperature (Tg) as the temperature is raised. However, in the case where xe2x80x9csome physical stimulusxe2x80x9d to a resin component of rapid phase transition is a temperature change, a resin composition comprising a resin component of rapid phase transition and photocurable component shows no state termed xe2x80x9cglass transitionxe2x80x9d even though temperature is gradually elevated, (accordingly no glass transition temperature is observed.), and becomes solated with a rapid decrease in viscosity at a specific temperature (Tp) (FIG. 1).
Herein, a term xe2x80x9csome physical stimulusxe2x80x9d means such a temperature change and light irradiation, and, in the case of xe2x80x9ctemperature changexe2x80x9d, it may comprise a temperature change from high to low or from low to high.
xe2x80x9cGel distinguishable from the photocured portionxe2x80x9d means, for example, a photocured portion is insoluble while a non-photocured gelated portion is soluble when immersed in some solvent.
In the present specification, xe2x80x9ccomponentxe2x80x9d means an essential element in the entire resin composition for optical lithography for implementing the optical lithography, and the element (i.e. xe2x80x9ccomponentxe2x80x9d) may be a purified substance or a mixture.
xe2x80x9cLight irradiation over a mask patternxe2x80x9d is performed according to ice patterns formed on sliced parts of the three-dimensional shape of an article to be produced, and, in this invention, carried out by irradiating light over the mask pattern formed directly on the resin composition for optical lithography corresponding to the slice patterns.
xe2x80x9cIrradiation lightxe2x80x9d used for irradiation with light is a light having a specific wave length capable of photocuring the resin composition for optical lithography, and the ultraviolet ray, visible light, etc. may be used for photocurable components in general, while the ultraviolet ray is generally used. In this invention, the mask pattern is drawn directly on the resin with no distance between the mask and resin surface, so that no consideration is required for the diffusion of light. Therefore, the xe2x80x9cirradiation lightxe2x80x9d used in this invention need not be the parallel light as far as the light has a predetermined light intensity to photocure the resin composition for optical lithography.
Material for forming the xe2x80x9cmask patternsxe2x80x9d may be anything to reflect or absorb an xe2x80x9cirradiation lightxe2x80x9d as far as they are able to shade the xe2x80x9cirradiation lightxe2x80x9d used for the light irradiation. In this case, taking the convenience of drawing patterns into consideration, a liquid material is preferable since the xe2x80x9cmask patternxe2x80x9d is drawn directly on the resin, but a solid material such as powdered material may be employed as the occasion may demand.